Image sensor and image-capturing device that selects pixel signal for focal position

ABSTRACT

An image sensor includes: a first pixel having a first photoelectric conversion unit that photoelectrically converts light having entered therein, and a first light blocking unit that blocks a part of light about to enter the first photoelectric conversion unit; and a second pixel having a second photoelectric conversion unit that photoelectrically converts light having entered therein and a second light blocking unit that blocks a part of light about to enter the second photoelectric conversion unit, wherein: the first photoelectric conversion unit and the first light blocking unit are set apart from each other by a distance different from a distance setting apart the second photoelectric conversion unit and the second light blocking unit.

This is a divisional of U.S. patent application Ser. No. 17/736,531filed May 4, 2022, which in turn is a divisional of U.S. patentapplication Ser. No. 16/984,641 filed Aug. 4, 2020 (now U.S. Pat. No.11,353,775), which is a continuation of U.S. patent application Ser. No.16/064,879 filed Jun. 21, 2018 (now U.S. Pat. No. 10,778,879), which isa U.S. National Stage of International Patent Application No.PCT/JP2016/088750 filed Dec. 26, 2016, which claims the priority benefitof Japanese Patent Application No. 2015-254898 filed in Japan on Dec.25, 2015. The disclosure of each of the prior applications is herebyincorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to an image sensor and an image-capturingdevice.

BACKGROUND ART

There are image sensors known in the related art in which the distancebetween a microlens and the corresponding light blocking unit at a focusdetection pixel used to detect the focusing condition through the splitpupil method, is adjusted in correspondence to the position of the focusdetection pixel on the image-capturing surface (see, for instance, PTL1). However, there is an issue yet to be addressed in the technologydisclosed in PTL 1 in that the focus detection accuracy is bound todeteriorate when an interchangeable lens with a different exit pupilposition is mounted.

CITATION LIST Patent Literature

-   PTL 1: Japanese Laid Open Patent Publication No. 2012-43939

SUMMARY OF INVENTION

According to the 1st aspect, an image sensor comprises: a first pixelhaving a first photoelectric conversion unit that photoelectricallyconverts light having entered therein, and a first light blocking unitthat blocks a part of light about to enter the first photoelectricconversion unit; and a second pixel having a second photoelectricconversion unit that photoelectrically converts light having enteredtherein and a second light blocking unit that blocks a part of lightabout to enter the second photoelectric conversion unit, wherein: thefirst photoelectric conversion unit and the first light blocking unitare set apart from each other by a distance different from a distancesetting apart the second photoelectric conversion unit and the secondlight blocking unit.

According to the 2nd aspect, it is preferable that in the image sensoraccording to the 1st aspect, the first pixel includes a first microlensand the first photoelectric conversion unit photoelectrically convertslight having been transmitted through the first microlens; the secondpixel includes a second microlens and the second photoelectricconversion unit photoelectrically converts light having been transmittedthrough the second microlens; and the first microlens and the firstlight blocking unit are set apart from each other by the distancedifferent from the distance setting the second microlens apart from thesecond light blocking unit.

According to the 3rd aspect, it is preferable that in the image sensoraccording to the 1st or 2nd aspect, the first pixel includes a firstoutput unit that outputs a signal generated based upon an electriccharge generated by the first photoelectric conversion unit throughphotoelectrically converting light having been transmitted through anoptical system and having entered therein; the second pixel includes asecond output unit that outputs a signal generated based upon anelectric charge generated by the second photoelectric conversion unitthrough photoelectrically converting light having been transmittedthrough the optical system and entered therein; and at least one of thesignal output from the first output unit and the signal output from thesecond output unit is a signal used to execute control so as to set theoptical system at a position at which an image formed via the opticalsystem is in an in-focus state at the image sensor.

According to the 4th aspect, it is preferable that in the image sensoraccording to any one of the 1st through 3rd aspects, the first lightblocking unit has an area different from an area of the second lightblocking unit.

According to the 5th aspect, the image sensor according to any one ofthe 1st through 4th aspects may further comprise: a plurality of firstpixels and a plurality of second pixels; and wherein: the first lightblocking units included in at least two first pixels among the pluralityof first pixels have areas different from each other in correspondenceto positions at the image sensor; and the second light blocking unitsincluded in at least two second pixels among the plurality of secondpixels have areas different from each other in correspondence topositions at the image sensor.

According to the 6th aspect, it is preferable that in the image sensoraccording to the 5th aspect, the first light blocking unit included inthe first pixel located near a center of the image sensor, among theplurality of first pixels, has an area smaller than the area of thefirst light blocking unit included in the first pixel located near anedge of the image sensor; and the second light blocking unit included inthe second pixel located near the center of the image sensor, among theplurality of second pixels, has an area smaller than the area of thesecond light blocking unit included in the second pixel located near anedge of the image sensor.

According to the 7th aspect, it is preferable that in the image sensoraccording to any one of the 1st through 6th aspects, the first pixelincludes a third light blocking unit that blocks part of light about toenter the first photoelectric conversion unit; and the second pixelincludes a fourth light blocking unit that blocks part of light about toenter the second photoelectric conversion unit.

According to the 8th aspect, it is preferable that in the image sensoraccording to the 7th aspect, the first light blocking unit has an areadifferent from an area of the third light blocking unit; and the secondlight blocking unit has an area different from an area of the fourthlight blocking unit.

According to the 9th aspect, it is preferable that in the image sensoraccording to the 8th aspect, the first light blocking unit has an areagreater than the area of the third light blocking unit; and the secondlight blocking unit has an area greater than the area of the fourthlight blocking unit.

According to the 10th aspect, it is preferable that in the image sensoraccording to any one of the 1st through 9th aspects, the first lightblocking unit is a circuit wiring disposed in the first pixel and thesecond light blocking unit is a circuit wiring disposed in the secondpixel.

According to the 11th aspect, the image sensor according to any one ofthe 1st through 10th aspects may further comprises: a plurality of firstpixels, a plurality of second pixels and a third pixel having a thirdphotoelectric conversion unit that photoelectrically converts lighthaving entered therein; and wherein the third pixel is disposed at leastone of between the plurality of first pixels and between the pluralityof second pixels.

According to the 12th aspect, it is preferable that in the image sensoraccording to any one of the 1st through 11th aspects, a plurality offirst pixels and a plurality of second pixels are disposed; at least twofirst pixels among the plurality of first pixels are disposed adjacentto each other; and at least two second pixels among the plurality ofsecond pixels are disposed adjacent to each other.

According to the 13th aspect, it is preferable that in the image sensoraccording to the 12th aspect, the two first pixels disposed adjacent toeach other share the first light blocking unit, or the two second pixelsdisposed adjacent to each other share the second light blocking unit.

According to the 14th aspect, the image sensor according to any one ofthe 1st through 13th aspects may further comprises: a plurality of firstpixels and a plurality of second pixels; and wherein the first pixelsare disposed in a quantity different from a quantity of the secondpixels.

According to the 15th aspect, an image-capturing device comprises: animage sensor having disposed thereat; a first pixel that includes afirst photoelectric conversion unit photoelectrically converting lighthaving been transmitted through an optical system and entered therein soas to generate an electric charge, and a first light blocking unit thatblocks part of light about to enter the first photoelectric conversionunit, set apart from the first photoelectric conversion unit by a firstdistance; and a second pixel that includes a second photoelectricconversion unit photoelectrically converting light having beentransmitted through the optical system and entered therein so as togenerate an electric charge, and a second light blocking unit thatblocks part of light about to enter the second photoelectric conversionunit, set apart from the second photoelectric conversion unit by asecond distance; and a control unit that controls a position of theoptical system so as to set the optical system at a position at which animage formed via the optical system is in an in-focus state at the imagesensor, by using at least one of a signal generated based upon theelectric charge generated at the first pixel and a signal generatedbased upon the electric charge generated at the second pixel.

According to the 16th aspect, it is preferable that in theimage-capturing device according to the 15th aspect, the image sensorincludes a plurality of first pixels and a plurality of second pixels;and the control unit controls the position of the optical system byusing at least one of signals generated based upon electric chargesgenerated at the plurality of first pixels and signals generated basedupon electric charges generated at the plurality of second pixels.

According to the 17th aspect, it is preferable that in theimage-capturing device according to the 15th or 16th aspect, the controlunit controls the position of the optical system by selecting, basedupon information regarding the optical system, at least one of thesignal generated based upon the electric charge generated at the firstpixel and the signal generated based upon the electric charge generatedat the second pixel.

According to the 18th aspect, it is preferable that in theimage-capturing device according to the 17th aspect, the image sensorincludes a plurality of focus detection areas each containing the firstpixel and the second pixel; and further comprises a selection unit thatis able to select any focus detection area among the plurality of focusdetection areas; and wherein if the selection unit selects a focusdetection area located near a center of the image sensor, the controlunit controls the position of the optical system by selecting, basedupon the information regarding the optical system, at least one of thesignal generated based upon the electric charge generated at the firstpixel and the signal generated based upon the electric charge generatedat the second pixel.

According to the 19th aspect, it is preferable that in theimage-capturing device according to the 17th or 18th aspect, the controlunit controls the position of the optical system by applying weight toat least one of the signal generated based upon the electric chargegenerated at the first pixel and the signal generated based upon theelectric charge generated at the second pixel.

According to the 20th aspect, the image-capturing device according toany one of the 15th through 19th aspects may further comprise: a storageunit in which information regarding the optical system is stored.

According to the 21st aspect, the image-capturing device according toany one of the 15th through 19th aspect may further comprise: areception unit that receives information regarding the optical system,provided from an interchangeable lens that includes the optical system.

According to the 22nd aspect, it is preferable that in theimage-capturing device according to the 20th or 21st aspect, theinformation regarding the optical system is information indicating aposition of an exit pupil of the optical system.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 The structure of the image-capturing device achieved in anembodiment, illustrated in a lateral sectional view

FIG. 2 A block diagram showing the essential structure of theimage-capturing device achieved in the embodiment

FIG. 3 Illustrations presenting an example of a positional arrangementwith which image-capturing pixels and focus detection pixels may bedisposed in the image sensor in the embodiment

FIG. 4 Examples of structures that may be adopted in the image-capturingpixels and the focus detection pixels, illustrated in schematicsectional views

FIG. 5 Illustrations, each indicating the position at which the lightblocking unit in a focus detection pixel is projected via the microlens

FIG. 6 Schematic illustrations, each indicating the relationship betweenlight fluxes entering focus detection pixels and the exit pupil areas atthe photographic optical system observed in the embodiment

FIG. 7 Examples of light blocking units that may be included in focusdetection pixels achieved in a variation

FIG. 8 Other examples of structures that may be adopted in focusdetection pixels, illustrated in schematic sectional views

FIG. 9 Other examples of structures that may be adopted in focusdetection pixels, illustrated in schematic sectional views

DESCRIPTION OF EMBODIMENT

In reference to drawings, the image sensor achieved in an embodiment,and a focus detection device and an image-capturing device, each havingthe image sensor installed therein, will be described.

The image-capturing device in the embodiment takes the form of a digitalcamera 100 structured as illustrated in the lateral sectional view inFIG. 1 . It is to be noted that a coordinate system that includes anx-axis, a y-axis and a z-axis is set as shown in the figure so as tofacilitate the explanation.

The digital camera 100 is a camera widely known as a mirrorless cameraconfigured with a camera body 200 and a photographic lens body 300, withthe photographic lens body 300 mounted via a mount unit (not shown).Photographic lens bodies 300 with various photographic optical systemscan be mounted at the camera body 200 via the mount unit. The mount unitincludes electrical contact points 201 and 202 and thus, an electricalconnection is achieved via the electrical contact points 201 and 202once the camera body 200 and the photographic lens body 300 becomecoupled.

A photographic optical system 1, a drive mechanism 3 and a lens dataunit 4 are disposed in the photographic lens body 300. The photographicoptical system 1 is an optical system via which a subject image isformed on the image-capturing surface of an image sensor 8 and isconfigured with a plurality of lenses including a focusing lens. Thedrive mechanism 3 calculates a lens drive quantity based upon a defocusquantity input from the camera body 200 via the electrical contact point201 and drives the focusing lens, constituting part of the photographicoptical system 1, to the focal position along the direction in which anoptical axis L extends (along the z-axis) in correspondence to the lensdrive quantity.

In the lens data unit 4 constituted with, for instance, a non-volatilerecording medium, various types of lens information related to thephotographic lens body 300, such as the position of the exit pupil inthe photographic optical system 1, are stored. The lens data unit 4transmits the lens information and the like to the camera body 200 viathe electrical contact point 202.

A control unit 5, an image sensor drive circuit 6, the image sensor 8,an electronic viewfinder (EVF) 9 and an eyepiece lens 10 are disposedinside the camera body 200. In addition, an operation unit 11 isdisposed at the camera body 200. Image-capturing pixels and focusdetection pixels, such as CCD or CMOS, are disposed in a two-dimensionalpattern (along rows and columns) over the x-y plane at the image sensor8. An image-capturing pixel receives a light flux having passed throughthe entire range of the exit pupil area at the photographic opticalsystem 1 and outputs an image signal to the control unit 5. A focusdetection pixel receives a light flux having passed through only part ofthe exit pupil area, e.g., a left side, a right side, an upper side or alower side of the exit pupil area, at the photographic optical system 1,and outputs a focus detection signal to the control unit 5. Theimage-capturing pixels at the image sensor 8 each include an R (red)color filter, a G (green) color filter or a B (blue) color filterdisposed thereat. Since the image-capturing pixels capture a subjectimage via the color filters, the image-capturing signals contain colorinformation expressed in the RGB colorimetric system. It is to be notedthat the focus detection pixels do not need to include color filters orcolor filters of a single type (e.g., G color filters) may be disposedat all the focus detection pixels. It is also to be noted that the imagesensor 8 will be described in detail later.

At the electronic viewfinder 9, an image corresponding to display imagedata generated by the control unit 5 is displayed. In addition, theelectronic viewfinder 9 provides display of various types of information(such as the shutter speed, the aperture value and the ISO sensitivity)related to photographing conditions. The user is able to view the imageand the various types of information displayed at the electronicviewfinder 9 via the eyepiece lens 10. It is to be noted that the imageand the various types of information may be displayed at a backsidemonitor (not shown).

The operation unit 11 includes various switches, each disposed incorrespondence to one of various operation members operated by the user,and outputs an operation signal, which corresponds to the user operationperformed at an operation member, to the control unit 5. The operationmembers include, for instance, a shutter release button, a menu buttonoperated to bring up a menu screen at the backside monitor (not shown)located on the back side of the camera body 200, a cross-key operated toselect various settings and the like, an OK button operated to confirm asetting or the like selected via the cross-key, an operation modeselector button operated to switch to an operation in a photographingmode or in a reproduction mode for the digital camera 1 and an exposuremode selector button operated to set an exposure mode.

The control system in the digital camera 100 will be explained inreference to the block diagram presented in FIG. 2 . As shown in FIG. 2, the digital camera 100 includes an A/D conversion unit 12, an imageprocessing circuit 13, a focus detection operation circuit 14, abody-lens communication unit 15 and a storage unit 16. The control unit5, which includes a CPU, a ROM, a RAM and the like, is an arithmeticoperation circuit that controls various components of the digital camera100 and executes various types of data processing based upon a controlprogram. The control program is stored in a non-volatile memory (notshown) within the control unit 5. The control unit 5 includes aselection unit 51, realized in the form of a functional unit, andselects focus detection pixels that are to output focus detectionsignals to be used for purposes of focus detection operation, among thefocus detection pixels in the image sensor 8. It is to be noted that theselection unit 51 will be described in specific detail later. The imagesensor drive circuit 6, which is controlled by the control unit 5,engages the image sensor 8 in electric charge storage, image-capturingsignal read out and the like by controlling the drive of the imagesensor 8 and the drive of the A/D conversion unit 12. The A/D conversionunit 12 converts analog image-capturing signals, output from the imagesensor 82, to digital signals.

The image-capturing signals output from the image-capturing pixels inthe image sensor 8 are used as image signals by the image processingcircuit 13, which generates image data by executing various types ofimage processing on the image signals and then generates an image fileby appending additional information and the like to the image data. Theimage processing circuit 13 records the image file thus generated into arecording medium such as a memory card (not shown). The image processingcircuit 13 generates display image data to be used to be displayed atthe electronic viewfinder 9 or the backside monitor (not shown) basedupon image data it has generated or image data recorded in the recordingmedium.

The focus detection operation circuit 14 calculates a defocus quantitythrough the phase detection method of the known art by using the focusdetection signals output from focus detection pixels in the image sensor8. The body-lens communication unit 15, which is controlled by thecontrol unit 5, engages in communication with the drive mechanism 3 andthe lens data unit 4 within the photographic lens body 300 via theelectrical contact points 201 and 202 so as to transmit camerainformation (such as the defocus quantity and an aperture value) andreceive lens information (e.g., the position of the exit pupil).

In the storage unit 16, which may be, for instance, a non-volatilestorage medium, a program that enables the control unit 5 to executevarious types of processing, data used by the control unit 5 when itexecutes the various types of processing and the like are stored.

Next, the image sensor 8 achieved in the embodiment will be described indetail.

FIG. 3(a) schematically illustrates an image-capturing surface 800 ofthe image sensor 8. It is to be noted that a coordinate system thatincludes the x-axis, the y-axis and the z-axis is set in FIG. 3 , inmuch the same way as in the example presented in FIG. 1 . Focusdetection areas 810, from which focus detection signals to be used inthe arithmetic operation executed to calculate the defocus quantity areobtained, are set at the image-capturing surface 800. It is to be notedthat while nine focus detection areas 810 are set in the examplepresented in the figure, the number of focus detection areas 810 is notlimited to this example.

FIG. 3(b) shows part of a focus detection area 810 a, set at theperiphery of the image-capturing surface 800 on the + side along thex-axis, in a schematic enlargement. The focus detection area 810 acontains a first pixel group 851, a second pixel group 852 and a thirdpixel group 853 (may each be generically referred to as a pixel group850). It is to be noted that while the pixel groups 850 are disposedover three rows in the example presented in FIG. 3(b), pixel groups donot need to be disposed over three rows. In addition, the order withwhich the first pixel group 851, the second pixel group 852 and thethird pixel group 853 are set along the y-axis is not limited to that inthe example presented in FIG. 3(b) and they may be disposed in anyorder. The differences among the first pixel group 851, the second pixelgroup 852 and the third pixel group 853 will be explained later.

In a pixel group 850, the position next to an image-capturing pixel 80on a given side along the x-axis is alternately taken by a focusdetection pixel 81 or a focus detection pixel 82, i.e., image-capturingpixels 80 are each disposed between a plurality of focus detectionpixels 81. In other words, the pixel group 850 extends along the x-axis.The first pixel group 851, the second pixel group 852 and the thirdpixel group 853 are set apart from each other along the y-axis.Image-capturing pixels 80 are disposed in the area separating the firstpixel group 851 and the second pixel group 852 from each other along they-axis and in the area separating the second pixel group 852 and thethird pixel group 853 from each other along the y-axis.

The first pixel group 851, the second pixel group 852 and the thirdpixel group 853 in the embodiment are configured so that focus detectionsignals can be output from the focus detection pixels 81 and 82 in theindividual pixel groups in correspondence to exit pupil positionsdifferent from one another, that may be taken at the photographicoptical system 1. Accordingly, the light blocking units in the firstpixel group 851, the second pixel group 852 and the third pixel group853 take positions different from one another. The following is adescription of the structures adopted in the image-capturing pixels 80and the focus detection pixels 81 and 82 included in the first pixelgroup 851, the second pixel group 852 and the third pixel group 853.

FIG. 4(a) schematically illustrates the structures of theimage-capturing pixels 80 and the focus detection pixels 81 and 82included in the first pixel group 851 in a sectional view, FIG. 4(b)schematically illustrates the structures of the image-capturing pixels80 and the focus detection pixels 81 and 82 included in the second pixelgroup 852 in a sectional view, and FIG. 4(c) schematically illustratesthe structures of the image-capturing pixels 80 and the focus detectionpixels 81 and 82 included in the third pixel group 853 in a sectionalview. It is to be noted that in FIG. 4 , too, a coordinate system thatincludes the x-axis, the y-axis and the z-axis is set, in much the sameway as in the examples presented in FIG. 1 and FIG. 3 .

—First Pixel Group 851 —

The focus detection pixels 81 in the first pixel group 851 each includea microlens 811, a photoelectric conversion unit 812 disposed below themicrolens 811, and a light blocking unit 813. The light blocking unit813 is disposed between the microlens 811 and the photoelectricconversion unit 812. A light flux, having departed the photographicoptical system 1 and passed through the microlens 811, enters thephotoelectric conversion unit 812 with part of the light flux blocked(restricted) by the light blocking unit 813.

The light blocking unit 813 is constituted with a circuit wiring for thefocus detection pixel 81, which may be manufactured by using anelectrically conductive material such as aluminum. The light blockingunit 813 restricts light that would otherwise travel toward the + sideof the x-axis in the focus detection pixel 81. The light blocking unit813 includes a first light blocking portion 813 a, a second lightblocking portion 813 b and a third light blocking portion 813 c setapart from the microlens 811 over distances different from one another.In the embodiment, the distance between the microlens 811 and the secondlight blocking portion 813 b is set greater than the distance betweenthe microlens 811 and the first light blocking portion 813 a. Thedistance between the microlens 811 and the third light blocking portion813 c is a set greater than the distance between the microlens 811 andthe second light blocking portion 813 b.

In the focus detection pixel 81 in the first pixel group 851, the thirdlight blocking portion 813 c has an area (i.e., a light blocking area)on a plane ranging parallel to the X-Y plane, which is greater than thecorresponding light blocking areas of the first light blocking portion813 a and the second light blocking portion 813 b. In other words, thelight flux is restricted by the third light blocking portion 813 c, setapart from the microlens 811 by the greatest distance, at the focusdetection pixel 81.

The focus detection pixels 82 in the first pixel group 851 each includea microlens 821, a photoelectric conversion unit 822 disposed below themicrolens 821, and a light blocking unit 823. The microlens 821 has afocal length equal to that of the microlens 811 in the focus detectionpixel 81. The distance between the photoelectric conversion unit 822 andthe microlens 821 is equal to the distance between the photoelectricconversion unit 812 and the microlens 811 at the focus detection pixel81. The light blocking unit 823 is disposed between the microlens 821and the photoelectric conversion unit 822. A light flux, having departedthe photographic optical system 1 and passed through the microlens 821,enters the photoelectric conversion unit 822 with part of the light fluxblocked (restricted) by the light blocking unit 823.

The light blocking unit 823 is constituted with a circuit wiring for thefocus detection pixel 82, which may be manufactured by using anelectrically conductive material such as aluminum. The light blockingunit 823 restricts light that would otherwise travel toward the − sideof the x-axis in the focus detection pixel 82. The light blocking unit823 includes a first light blocking portion 823 a, a second lightblocking portion 823 b and a third light blocking portion 823 c setapart from the microlens 821 over distances different from one another.In the embodiment, the distance between the microlens 821 and the secondlight blocking portion 823 b is set greater than the distance betweenthe microlens 821 and the first light blocking portion 823 a. Thedistance between the microlens 821 and the third light blocking portion823 c is a set greater than the distance between the microlens 821 andthe second light blocking portion 823 b. The distance between the thirdlight blocking portion 823 c and the microlens 821 is equal to thedistance between the third light blocking portion 813 c and themicrolens 811 at the focus detection pixel 81.

At the focus detection pixel 82, too, the third light blocking portion823 c has an area (i.e., a light blocking area) on a plane rangingparallel to the X-Y plane, which is greater than the corresponding lightblocking areas of the first light blocking portion 823 a and the secondlight blocking portion 823 b. In other words, the light flux isrestricted by the third light blocking portion 823 c, set apart from themicrolens 821 by the greatest distance, at the focus detection pixel 81.

In the first pixel group 851, which includes the focus detection pixels81 and 82 structured as described above, light fluxes having departeddifferent areas of the photographic optical system 1 are restricted bythe third light blocking portions 813 c and 823 c set apart from themicro-lenses 811 and 821 over distances equal to each other. Namely,light fluxes having departed different areas of the photographic opticalsystem 1, enter the photoelectric conversion units 812 and 822 at thepair of focus detection pixels 81 and 82 in the first pixel group 851,as a pair of subject light fluxes to be used by the focus detectionoperation circuit 14 for a phase detection operation.

The image-capturing pixels 80 each include a microlens 801 and aphotoelectric conversion unit 802 disposed below the microlens 801. Alight flux having passed through the entire range of the photographicoptical system 1 enters the photoelectric conversion unit 802 via themicrolens 801. It is to be noted that the image-capturing pixels 80disposed in the second pixel group 852 and the third pixel group 853assume a structure identical to that described above. In addition,image-capturing pixels 80 disposed outside the pixel groups 850, too,assume a structure identical to that described above.

—Second Pixel Group 852 —

The focus detection pixels 81 and 82 included in the second pixel group852 will be described by focusing on the differences from the focusdetection pixels 81 and 82 in the first pixel group 851. Any featuresnot specifically noted are assumed to be identical to those of the focusdetection pixels 81 and 82 in the first pixel group 851. At each focusdetection pixel 81 in the second pixel group 852, the second lightblocking portion 813 b has a light blocking area, on a plane rangingparallel to the X-Y plane, which is greater than the corresponding lightblocking areas of the first light blocking portion 813 a and the thirdlight blocking portion 813 c. In other words, entry of light towardthe + side along the x-axis is restricted at the focus detection pixel81 by the second light blocking portion 813 b disposed between the firstlight blocking portion 813 a and the third light blocking portion 813 c,viewed from the side where the microlens 821 is located.

At each focus detection pixel 82 in the second pixel group 852, thesecond light blocking portion 823 b has a light blocking area, on aplane ranging parallel to the X-Y plane, which is greater than thecorresponding light blocking areas of the first light blocking portion823 a and the third light blocking portion 823 c. In other words, entryof light toward the − side along the x-axis is restricted at the focusdetection pixel 82 by the second light blocking portion 823 b disposedbetween the first light blocking portion 823 a and the third lightblocking portion 823 c, viewed from the side where the microlens 821 islocated. In the second pixel group 852, which includes the focusdetection pixels 81 and 82 structured as described above, light fluxeshaving departed different areas of the photographic optical system 1 arerestricted by the second light blocking portions 813 b and 823 b setapart from the micro-lenses 811 and 821 over distances equal to eachother. Namely, light fluxes, having departed different areas of thephotographic optical system 1, enter the photoelectric conversion units812 and 822 at the pair of focus detection pixels 81 and 82 in thesecond pixel group 852, as a pair of subject light fluxes to be used bythe focus detection operation circuit 14 for a phase detectionoperation.

—Third Pixel Group 853 —

The focus detection pixels 81 and 82 included in the third pixel group853 will be described by focusing on the differences from the focusdetection pixels 81 and 82 in the first pixel group 851. Any featuresnot specifically noted are assumed to be identical to those of the focusdetection pixels 81 and 82 in the first pixel group 851. At each focusdetection pixel 81 in the third pixel group 853, the first lightblocking portion 813 a has a light blocking area, on a plane rangingparallel to the X-Y plane, which is greater than the corresponding lightblocking areas of the second light blocking portion 813 b and the thirdlight blocking portion 813 c. In other words, entry of light towardthe + side along the x-axis is restricted at the focus detection pixel81 by the first light blocking portion 813 a set apart from themicrolens 821 by the smallest distance.

At each focus detection pixel 82 in the third pixel group 853, the firstlight blocking portion 823 a has a light blocking area, on a planeranging parallel to the X-Y plane, which is greater than thecorresponding light blocking areas of the second light blocking portion823 b and the third light blocking portion 823 c. In other words, entryof light toward the − side along the x-axis is restricted by the firstlight blocking portion 823 a, set apart from the microlens 821 by thesmallest distance. In the third pixel group 853, which includes thefocus detection pixels 81 and 82 structured as described above, lightfluxes having departed different areas of the photographic opticalsystem 1 are restricted by the first light blocking portions 813 a and823 a set apart from the micro-lenses 811 and 821 over distances equalto each other. Namely, light fluxes, having departed different areas ofthe photographic optical system 1, enter the photoelectric conversionunits 812 and 822 at the pair of focus detection pixels 81 and 82 in thethird pixel group 853, as a pair of subject light fluxes to be used bythe focus detection operation circuit 14 for a phase detectionoperation.

As explained above, entry of light at the focus detection pixels 81 and82 is restricted via the light blocking units 813 and 823 at positions(over distances from the micro-lenses 811 and 821) different from oneanother among the first pixel group 851, the second pixel group 852 andthe third pixel group 853.

FIG. 5 schematically illustrates the relationship of the position atwhich the pupil of the photographic optical system 1 is projected via amicrolens 811 to the position of the corresponding light blocking unit813 along the z-axis, achieved in correspondence to each of threedifferent exit pupil positions PO1, PO2 and PO3

As FIG. 5(a) indicates, the pupil having the exit pupil position PO1 atthe photographic optical system 1 is projected via the microlens 811onto the third light blocking portion 813 c of a focus detection pixel81 in the first pixel group 851. Namely, the third light blockingportion 813 c is disposed at a position at which the pupil having theexit pupil position PO1 is projected via the microlens 811. As FIG. 5(b)indicates, the pupil having the exit pupil position PO2 at thephotographic optical system 1 is projected via the microlens 811 ontothe second light blocking portion 813 b of a focus detection pixel 81 inthe second pixel group 852. Namely, the second light blocking portion813 b is disposed at a position at which the pupil having the exit pupilposition PO2 is projected via the microlens 811. As FIG. 5(c) indicates,the pupil having the exit pupil position PO3 at the photographic opticalsystem 1 is projected via the microlens 811 onto the first lightblocking portion 813 a of a focus detection pixel 81 in the third pixelgroup 853. Namely, the first light blocking portion 813 a is disposed ata position at which the pupil having the exit pupil position PO3 isprojected via the microlens 811. It is to be noted that the third lightblocking portion 813 c, the second light blocking portion 813 b and thefirst light blocking portion 813 a represent the entire light blockingunit in the illustrations presented in FIGS. 5(a), 5(b) and 5(c)respectively. In addition, at the focus detection pixels 82 havingstructures similar to those of the focus detection pixels 81 so that thefocus detection pixels 82 and the focus detection pixels 81 togetherachieve axial symmetry, relationships similar to those pertaining to theprojection positions taken at the light blocking units 813 in the focusdetection pixels 81 are achieved with regard to the projection positionstaken at the light blocking units 823.

The pupils having the different exit pupil positions PO1, PO2 and PO3are projected via microlenses 811 at positions different from oneanother among the individual pixel groups 850. This means that the focusdetection pixels in the first pixel group 851, the focus detectionpixels in the second pixel group 852 or the focus detection pixels inthe third pixel group 853 can be used as optimal focus detection pixelsfor purposes of focus detection in conjunction with a specificphotographic optical system 1 among photographic optical systems 1having different exit pupil positions.

FIG. 6 presents schematic illustrations, each indicating a relationshipof the photoelectric conversion units 812 and 822 in a focus detectionpixel 81 and a focus detection pixel 82 present in the second pixelgroup 852 to the position of an exit pupil 940 of the photographicoptical system 1. FIG. 6(a) shows the relationship achieved when aphotographic lens body 300, having a photographic optical system 1, thepupil of which, taking the exit pupil position PO2, is projected at aposition substantially matching the positions of the second lightblocking portions 813 b and 823 b of the focus detection pixels 81 and82 in the second pixel group 852, is mounted. In other words, it showsthe relationship achieved when the photographic optical system 1 has theexit pupil position PO2, which achieves a conjugal relationship with thesecond light blocking portions 813 b and 823 b relative to themicrolenses 811 and 821.

The photoelectric conversion unit 812 in the focus detection pixel 81receives, via the microlens 811, a light flux 951 having departed thesubject and passed through an exit pupil area 941 a, i.e., one of thepair of exit pupil areas 941 a and 942 a at the photographic opticalsystem 1. This means that the light having departed the exit pupil area942 a is blocked by the second light blocking portion 813 b. Thephotoelectric conversion unit 822 in the focus detection pixel 82receives, via the microlens 821, a light flux 952 having departed thesubject and passed through the exit pupil area 942 a at the photographicoptical system 1. This means that the light having departed the exitpupil area 941 a is blocked by the second light blocking portion 823 b.As FIG. 6(a) indicates, the light fluxes 951 and 952 enter thephotoelectric conversion units 812 and 822 respectively with little orno vignetting attributable to the structure of the photographic lensbody 300.

FIG. 6(b) indicates the relationship achieved when a photographic lensbody 300, which includes a photographic optical system 1 having the exitpupil position PO3 set at a greater distance compared to thephotographic lens body 300 with the exit pupil position PO2, is mounted.In this case, the second light blocking portions 813 b and 823 b in thefocus detection pixels 81 and 82 block light having been transmittedthrough portions (areas) different from the exit pupil areas 941 a and942 a, which are part of the exit pupil 940 of the photographic opticalsystem 1 described above. It is to be noted that the exit pupil 940 ofthe photographic optical system 1 having the exit pupil position PO2 isindicated with dotted lines in FIG. 6(b) for purposes of easycomparison.

The light flux 952 having departed the subject passes through an exitpupil area 942 b at the photographic optical system 1 and then entersthe photoelectric conversion unit 822 via the microlens 821 at the focusdetection pixel 82. Since the exit pupil position PO3 by thephotographic optical system 1 is set at a greater distance compared tothe exit pupil position PO2, part of the light flux 951 having departedthe subject is vignetted. Namely, light flux 951 a in the light flux 951passes through an exit pupil area 941 b of the photographic opticalsystem 1 and enters the photoelectric conversion unit 812 via themicrolens 811, while light flux 951 b in the light flux 951 is vignettedand thus does not enter the photoelectric conversion unit 812. Thismeans that different amounts of light enter the photoelectric conversionunits 812 and 822 in the focus detection pixels 81 and 82 respectively,resulting in the focus detection pixel signal output from thephotoelectric conversion unit 812 being output at a lower output levelcompared to the output level of the focus detection signal output fromthe photoelectric conversion unit 822. In other words, if focusdetection pixels 81 having light blocking units via which light isblocked by the second light blocking portions 813 b are used inconjunction with the photographic optical system 1 having the exit pupilposition PO3, the arithmetic operation accuracy of the focus detectionoperation would be compromised.

In conjunction with the photographic optical system 1 having the exitpupil position PO3, it is ensured that the light fluxes having departedthe exit pupil areas 941 b and 942 b enter the focus detection pixels 81and 82 having the first light blocking portions 813 a and 823 a disposedat positions at which the pupil at the exit pupil position PO3 isprojected via the microlenses 811 and 821. As FIG. 6(c) illustrates,light enters the focus detection pixels 81 and 82 in the third pixelgroup 853 having disposed therein focus detection pixels 81 and 82 atwhich light is restricted by the first light blocking portions 813 a and823 a set apart from the microlenses 811 and 821 over the smallestdistance while allowing little or no vignetting as shown in FIG. 5(b).

In addition, it is ensured that light fluxes having departed exit pupilareas enter the focus detection pixels 81 and 82 with the third lightblocking portions 813 c and 823 c disposed at positions at which thepupil at, for instance, the exit pupil position PO1 is projected via themicrolenses 811 and 821 in conjunction with a photographic opticalsystem 1 having an exit pupil position set over a distance shorter thanPO2. In other words, it is ensured that the light fluxes having departedthe exit pupil areas enter the focus detection pixels 81 and 82 in thefirst pixel group 851, at which light is restricted by the third lightblocking portions 813 c and 823 c set apart from the microlenses 811 and821 over the greatest distance. This means that light is allowed toenter the photoelectric conversion units 812 and 822 in any one of thepixel groups 850 with little or no vignetting, even when a photographicoptical system 1 having a different exit pupil position is mounted.Thus, focus detection can be executed through the embodiment by usingfocus detection signals output from the focus detection pixels 81 and 82having received light with little or no vignetting even when a differentphotographic lens body 300 is mounted or when the photographic lens body300 is a zoom lens that includes a photographic optical system 1 with avariable exit pupil position.

It is to be noted that focus detection pixels 81 and 82 in the variouspixel groups 850 set in the focus detection area 810 b (see FIG. 3(a)),disposed at a position being symmetry with the focus detection area 810a relative to the center of the image-capturing surface 800, aredifferent from the focus detection pixels 81 and 82 disposed in thefocus detection area 810 a. Namely, a focus detection pixel 82 isdisposed in the focus detection area 810 b at a position being symmetryto a focus detection pixel 81 in the focus detection area 810 a relativeto the center of the image-capturing surface 800. A focus detectionpixel 81 is disposed at a position being symmetry to a focus detectionpixel 82 in the focus detection area 810 a relative to the center of theimage-capturing surface 800.

In each pixel group 850 set in the focus detection area 810 a, the focusdetection pixels 81 and 82 disposed toward the − side end along thex-axis and the focus detection pixels 81 and 82 disposed toward the +side end along the x-axis are affected differently by oblique incidenceof light having passed through the photographic optical system 1. Forthis reason, the light blocking units 813 and 823 in the focus detectionpixels 81 and 82 disposed toward the + side end along the x-axis need tohave a light blocking area, ranging along the x-axis, greater than thelight blocking area of the light blocking units 813 and 823 of the focusdetection pixels 81 and 82 disposed toward the − side end along thex-axis. The extent by which the light blocking area needs to increasecan be determined by multiplying the distance to the focus detectionpixels 81 and 82 measured from the center of the image-capturing surface800, i.e., the image height, by a predetermined coefficient. In thiscase, the light blocking area of the light blocking units 813 and 823may be made to increase linearly along the x-axis for pixels atpositions closer to the + side end along the x-axis in the pixel group850, or the light blocking area of the light blocking units 813 and 823may be made to increase along the x-axis in steps, with each stepcorresponding to a predetermined number of focus detection pixels 81 and82.

In each pixel group 850 in the focus detection area 810 b, the lightblocking units 813 and 823 in the focus detection pixels 81 and 82disposed toward the − side end along the x-axis have a greater lightblocking area, measured along the x-axis, in comparison to the lightblocking area of the light blocking units 813 and 823 in the focusdetection pixels 81 and 82 disposed toward the + side end along thex-axis. In this case, too, the light blocking area of the light blockingunits 813 and 823 may be made to increase linearly along the x-axis forpixels at positions closer to the + side end along the x-axis in thepixel group 850, or the light blocking area of the light blocking units813 and 823 may be made to increase along the x-axis in steps, with eachstep corresponding to a predetermined number of focus detection pixels81 and 82. This means that the positional relationship along the x-axis,which extends perpendicular to the optical axes of the microlenses 811and 812, between the light blocking units 813 and 823 of the focusdetection pixels 81 and 82 disposed toward one end along the x-axis andthe corresponding microlenses 811 and 812 in a pixel group 850 isdifferent from the positional relationship of the light blocking units813 and 823 in the focus detection pixels 81 and 82 disposed toward theother end, to the microlenses 811 and 812, along the x-axis extendingperpendicular to the optical axes of the microlenses 811 and 812.

It is to be noted that light is not vignetted in the focus detectionarea 810 c (see FIG. 3(a)) set in a central area of the image-capturingsurface 800 of the image sensor 8 and for this reason, the lightblocking units 813 and 823 do not need to have greater light blockingareas.

In addition, a given type of pixel group 850 may be disposed in agreater quantity in a focus detection area 810 set in a peripheral areaof the image-capturing surface 800 of the image sensor 8, compared tothe quantity of the particular pixel group 850 included in a focusdetection area 810 set in a central area of the image-capturing surface800, or a given type of pixel group 850 may be disposed with higherdensity in a focus detection area 810 set in a peripheral area. Forinstance, the first pixel group 851 and the third pixel group 853 may beset in greater quantities or with higher density relative to the secondpixel group 852 in a focus detection area 810 on the periphery. Inaddition, the quantities of the first pixel group 851 and the thirdpixel group 853 may be increased or they may be disposed with evenhigher density in a focus detection area 810 located further toward theouter edge.

As an alternative, the first pixel group 851 having the focus detectionpixels 81 and 82 corresponding to the exit pupil position PO3 shown inFIG. 5(c), may be disposed in greater quantity or with higher density,in comparison to the third pixel group 853 having the focus detectionpixels 81 and 82 corresponding to the exit pupil position PO1 shown inFIG. 5(a). This means that the third pixel group 853 may be disposed ina smaller quantity or with lower density relative to the first pixelgroup 851. When a photographic lens body 300 with a photographic opticalsystem 1 having an exit pupil position set at a greater distance (e.g.,a telephoto lens) is mounted, an offset occurring at the focal positionis bound to be more noticeable due to a smaller photographic depth offield. In contrast, when a photographic lens body 300 with aphotographic optical system 1 having an exit pupil position set over asmaller distance (e.g., a wide-angle lens) is mounted, an offsetoccurring at the focal position is not readily noticeable because of agreater photographic depth of field. Accordingly, by disposing the firstpixel group 851 corresponding to the exit pupil position PO3 in agreater quantity or with higher density, the extent to which focusdetection accuracy is lowered can be minimized even when a photographiclens 300 with an exit pupil position set at a greater distance ismounted in the digital camera 100.

As an alternative, a pixel group 850 with focus detection pixels 81 and82 corresponding to the exit pupil position of the photographic opticalsystem 1 included in a photographic lens body 300 (e.g., a standard lensor a wide-angle lens) that is frequently used by the user may bedisposed in greater quantity or with higher density within the focusdetection areas 810.

The focus detection operation executed in the digital camera 100equipped with the image sensor 8 structured as described above will beexplained next.

As the photographic lens body 300 is mounted at the camera body 200, anelectrical connection between the camera body 200 and the photographiclens body 300 is established via the electrical contact points 201 and202 disposed at the mount unit. The body-lens communication unit 15receives the lens information, i.e., information regarding the exitpupil position, from the lens data unit 4 in the photographic lens body300, via the electrical contact points 201 and 202.

The selection unit 51 in the control unit 5 selects, based upon the lensinformation received from the photographic lens body 300, a pixel group850 having focus detection pixels 81 and 82 best suited for thephotographic optical system 1 included in the mounted photographic lensbody 300. If the value representing the position of the exit pupil atthe photographic optical system 1 exceeds a predetermined firstthreshold value, the selection unit 51 selects the third pixel group 853that includes focus detection pixels 81 and 82 having the light blockingunits 813 and 823 set apart from the microlenses 811 and 821 over thesmallest distance. If the value representing the exit pupil position atthe photographic optical system 1 is less than a predetermined secondthreshold value (<first threshold value), the selection unit 51 selectsthe first pixel group 851 that includes focus detection pixels 81 and 82having the light blocking units 813 and 823 set apart from themicrolenses 811 and 821 over the greatest distance. If the valuerepresenting the exit pupil position at the photographic optical system1 is equal to or greater than the second threshold value and less thanthe first threshold value, the selection unit 51 selects the secondpixel group 852. In other words, the selection unit 51 selects aspecific type of pixel group 850 that includes focus detection pixels 81and 82 having focus detection pupil positions with the smallestdifference relative to the exit pupil position at the photographicoptical system 1.

It is to be noted that the selection unit 51 is able to select a pixelgroup 850 within a given focus detection area 810 by switching to anoptimal quantity of, or an optimal type of pixel group based upon theposition of the particular focus detection area 810 on theimage-capturing surface 800 of the image sensor 8 or based upon theposition of the exit pupil at the photographic optical system 1.

In addition, when a photographic lens body 300 configured with a zoomlens is mounted, the position of the exit pupil changes incorrespondence to the zoom position. In such a case, the selection unit51 obtains information indicating the exit pupil position correspondingto the selected zoom setting based upon the lens information having beenreceived and selects the pixel group 850 best suited to the exit pupilposition indicated in the information having been obtained as describedabove. Through these measures, the pixel group 850 to be selected can beautomatically switched by the selection unit 851 based upon the selectedzoom setting. Information indicating exit pupil positions correspondingto different zoom settings is stored in advance in the lens data unit 4.It is to be noted that information indicating exit pupil positionscorresponding to different zoom settings may be instead stored inadvance in the storage unit 16 in the digital camera 100. In addition,when executing focus detection based upon an output provided from afocus detection area 810 located near the center of the image-capturingsurface 800 of the image sensor 8 (from the focus detection area 810 ain FIG. 3(a)), the selection unit 851 may select the focus detectionpixels 81 and 82 included in the first pixel group 851, the second pixelgroup 852 and the third pixel group 853. In this case, improvement willbe obtained in focus detection accuracy in the subject trackingperformance and in the subject identification performance. Whenexecuting focus detection based upon an output provided from a focusdetection area 810 taking a peripheral position in the image-capturingsurface 800 of the image sensor 8, the selection unit 851 selects onlythe pixel group 850 that includes the focus detection pixels 81 and 82corresponding to the exit pupil position at the photographic opticalsystem 1. In the peripheral area of the image-capturing surface 800,outputs from focus detection pixels 81 and 82 other than the focusdetection pixels 81 and 82 corresponding to the exit pupil position atthe photographic optical system 1 are bound to be affected by vignettingand the like. Accordingly, the outputs from the focus detection pixels81 and 82 affected by vignetting and the like are not used for purposesof focus detection so as to minimize the extent to which the focusdetection accuracy is lowered.

The focus detection operation circuit 14 calculates a defocus quantitythrough a phase detection method of the known art by using the focusdetection signals output from the focus detection pixels 81 and 82 in aselected pixel group 850, among the focus detection signals output fromall the focus detection pixels 81 and 82. The focus detection operationcircuit 14 detects an extent of offset of a first signal train {an}having set therein in sequence the focus detection signals output fromthe photoelectric conversion units 812 in the focus detection pixels 81relative to a second signal train {bn} having set therein in sequencethe focus detection signals output from the photoelectric conversionunits 822 in the focus detection pixels 82, and detects the focusingcondition at the photographic optical system 1 represented by thedefocus quantity. In other words, once the selection unit 851 selectsfocus detection pixels 81 and 82 as described above, the focus detectionoperation circuit 14 detects the position at which an image formed viathe photographic optical system 1 achieves an in-focus state at theimage sensor 8 based upon at least one set of outputs among the set ofoutputs from the focus detection pixels 81 and 82 in the first pixelgroup 851, the set of outputs from the focus detection pixels 81 and 82in the second pixel group 852 and the set of outputs from the focusdetection pixels 81 and 82 in the third pixel group 853.

The following advantages and operations are achieved through theembodiment described above.

-   -   (1) In each pixel group 850, focus detection pixels 81 and 82        that receive light fluxes having passed through pupil areas,        i.e., portions of the pupil, of the photographic optical system        1, are disposed along the x-axis. Third light blocking portions        813 c and 823 c included in the focus detection pixels 81 and 82        in the first pixel group 851 are disposed between the        microlenses 811 and 822 and the photoelectric conversion units        812 and 822 and restrict light having passed through specific        exit pupil areas, i.e., portions of the exit pupil, of the        photographic optical system 1. Second light blocking portions        813 b and 823 b included in the focus detection pixels 81 and 82        in the second pixel group 852 are disposed between the        microlenses 811 and 822 and the photoelectric conversion units        812 and 822 and restrict light having passed through specific        exit pupil areas, i.e., portions of the exit pupil, of the        photographic optical system 1. First light blocking portions 813        a and 823 a included in the focus detection pixels 81 and 82 in        the third pixel group 853 are disposed between the microlenses        811 and 822 and the photoelectric conversion units 812 and 822        and restrict light having passed through specific exit pupil        areas, i.e., portions of the exit pupil, of the photographic        optical system 1. The distance to the third light blocking        portions 813 c and 823 c, measured from the microlenses 811 and        821 in the focus detection pixels 81 and 82 in the first pixel        group 851, the distance to the second light blocking portions        813 b and 823 b, measured from the microlenses 811 and 821 in        the focus detection pixels 81 and 82 in the second pixel group        852 and the distance to the first light blocking portions 813 a        and 823 a, measured from the microlenses 811 and 821 in the        focus detection pixels 81 and 82 in the third pixel group 853,        are different from one another. Thus, even when a photographic        optical system 1 with a different exit pupil position is        mounted, focus detection signals originating from the focus        detection pixels 81 and 82, at which light has entered without        significant vignetting and the like, among the focus detection        pixels in the various pixel groups 850, are output. In other        words, the extent to which the accuracy of focus detection        operation is lowered can be minimized.    -   (2) The light blocking units 813 and 823 are constituted with        circuit wirings. Since such circuit wirings can be shared with        other members, the number of required components can be kept        down.    -   (3) The microlenses 811 and 812 at the focus detection pixels 81        and 82 disposed in the various pixel groups have a uniform focal        length and the microlenses 811 and 821 are set apart from the        corresponding photoelectric conversion units 812 and 822 over a        uniform distance. This means that focus detection can be        executed in an optimal manner in conjunction with photographic        optical systems 1 with varying exit pupil distances simply by        disposing light blocking units 813 and 823 in the focus        detection pixels 81 and 82 adopting identical structures.    -   (4) The positional relationship of the light blocking units 813        and 823 to the microlenses 811 and 821, along the z-axis, in the        focus detection pixels 81 and 82 disposed toward one end (on the        − side along the x-axis) in each pixel group 850 set in a        peripheral area of the image-capturing surface 800 of the image        sensor 8 is different from the positional relationship of the        light blocking units 813 and 823 to the micro-lenses 811 and        821, along the z-axis, in the focus detection pixels 81 and 82        disposed toward the other end (on the + side along the x-axis)        in the pixel group. As a result, incident light obliquely        entering the peripheral area of the image-capturing surface 800        can be received at the photoelectric conversion units 812 and        822 with little or no vignetting. In addition, focus detection        can be executed in the peripheral area of the image-capturing        surface 800 of the image sensor 8.    -   (5) The focus detection operation circuit 14 detects the        focusing condition at the photographic optical system 1 by using        the focus detection signals output from the focus detection        pixels 81 and 82 in the first pixel group 851, the focus        detection signals output from the focus detection pixels 81 and        82 in the second pixel group, or the focus detection signals        output from the focus detection pixels 81 and 82 in the third        pixel group 853. A plurality of focus detection areas 810, to be        used for purposes of focusing condition detection, are set in        the image-capturing surface 800 of the image sensor 8 and pixel        groups 850 are present within the focus detection areas 810.        Accordingly, even when a photographic optical system 1 having a        different exit pupil position is mounted, a focus detection        operation can be executed by using focus detection signals        provided from focus detection pixels 81 and 82 that are not        significantly affected by vignetting and the like, within a        focus detection area 810.    -   (6) The selection unit 51 selects the first pixel group, the        second pixel group or the third pixel group based upon the lens        information regarding the position of the exit pupil in the        photographic optical system 1, and the focus detection operation        circuit 14 detects the focusing condition at the photographic        optical system 1 by using the focus detection signals output        from the focus detection pixels 81 and 82 present in the pixel        group 850 having been selected by the selection unit 51. Thus, a        focus detection operation can be executed by using the focus        detection signals output from the focus detection pixels 81 and        82 least affected by vignetting and the like, in a pixel group        among the plurality of pixel groups 850.

While the focus detection pixels 81 and 82 in the embodiment describedabove adopt the structures explained in reference to FIG. 4 , thepresent invention may be adopted in conjunction with focus detectionpixels 81 and 82 adopting structures other than those shown in FIG. 4 .

FIG. 8 presents schematic sectional views of the structures adopted infocus detection pixels 81 and 82 in another example. FIGS. 8(a), 8(b)and 8(c), similar to FIGS. 4(a), 4(b) and 4(c) respectively, illustratethe structures of image-capturing pixels 80 and focus detection pixels81 and 82 in a first pixel group 851, a second pixel group 852 and athird pixel group 853 (see FIG. 3(b)) respectively. It is to be notedthat in FIG. 8 , too, a coordinate system that includes the x-axis, they-axis and the z-axis is set, in much the same way as in the examplespresented in FIG. 1 and FIG. 3 .

The focus detection pixels 81 and 82 in the example presented in FIG. 8each include a single light blocking unit 813 or 823. The focusdetection pixels 81 and 82 in the first pixel group 851 shown in FIG.8(a) respectively include third light blocking portions 813 c and 823 c,similar to those shown in FIG. 4(a), but do not include the first lightblocking portions 813 a and 823 a and the second light blocking portions813 b and 823 b in FIG. 4(a). Namely, the focus detection pixels 81 and82 in FIG. 8(a) only include the third light blocking portions 813 c and823 c having the largest light blocking areas, among the light blockingportions in the light blocking units 813 and 823 shown in FIG. 4(a). Inthis case, too, light fluxes having departed the photographic opticalsystem 1 and passed through the microlenses 811 and 821, enter thephotoelectric conversion units 812 and 822 of the focus detection pixels81 and 82 with part of the light blocked (restricted) by the third lightblocking portions 813 c and 823 c.

The focus detection pixels 81 and 82 in the second pixel group 852 shownin FIG. 8(b) respectively include second light blocking portions 813 band 823 b, similar to those shown in FIG. 4(b), but do not include thefirst light blocking portions 813 a and 823 a and the third lightblocking portions 813 c and 823 c in FIG. 4(a). Namely, the focusdetection pixels 81 and 82 in FIG. 8(b) only include the second lightblocking portions 813 b and 823 b having the largest light blockingareas, among the light blocking portions in the light blocking units 813and 823 shown in FIG. 4(b). In this case, too, light fluxes havingdeparted the photographic optical system 1 and passed through themicrolenses 811 and 821, enter the photoelectric conversion units 812and 822 of the focus detection pixels 81 and 82 with part of the lightblocked (restricted) by the second light blocking portions 813 b and 823b.

The focus detection pixels 81 and 82 in the third pixel group 853 shownin FIG. 8(c) respectively include first light blocking portions 813 aand 823 a, similar to those shown in FIG. 4(c) but do not include thesecond light blocking portions 813 b and 823 b and the third lightblocking portions 813 c and 823 c in FIG. 4(c). Namely, the focusdetection pixels 81 and 82 in FIG. 8(a) only include the first lightblocking portions 813 a and 823 a having the largest light blockingareas, among the light blocking portions in the light blocking units 813and 823 shown in FIG. 4(c). In this case, too, light fluxes havingdeparted the photographic optical system 1 and passed through themicrolenses 811 and 821, enter the photoelectric conversion units 812and 822 of the focus detection pixels 81 and 82 with part of the lightblocked (restricted) by the first light blocking portions 813 a and 823a.

The focus detection pixels 81 and 82 adopting the structures describedabove in the alternative example presented in FIG. 8 , make it possibleto restrict light having departed the photographic optical system 1 inmuch the same way as that described in reference to the embodiment,while also making it possible to reduce the number of requiredcomponents.

It is to be noted that the light blocking units 813 and 823 in the focusdetection pixels 81 and 82 do not need to each include only one lightblocking portion as in the example shown in FIGS. 8(a) through 8(c). Forinstance, the focus detection pixels 81 in the first pixel group 851 mayeach include a light blocking unit 813 constituted with a first lightblocking portion 813 a, a second light blocking portion 813 b and athird light blocking portion 813 c as illustrated in FIG. 8(d), in muchthe same way as the focus detection pixel 81 in FIG. 4(a). The focusdetection pixels 82, on the other hand, may each include a lightblocking unit 823 constituted with a third light blocking portion 823 calone without a first light blocking portion 823 a or a second lightblocking portion 823 b. In this case, too, light having departed thephotographic optical system 1 can be blocked (restricted) by the thirdlight blocking portions 813 c and 823 c, as in the focus detectionpixels 81 and 82 described in reference to the embodiment. It is to benoted that as an alternative to the example presented in FIG. 8(d),focus detection pixels 81, each having a light blocking unit 813constituted with a single light blocking portion, and focus detectionpixels 82, each having a light blocking unit 823 constituted with aplurality of light blocking portions, as shown in FIG. 4(a), may beused. In addition, while structures that may be adopted in the focusdetection pixels 81 and 82 in the first pixel group 851 have beendescribed in reference to FIG. 8(d), the structures explained above maybe adopted in focus detection pixels 81 and 82 disposed in the secondpixel group 852 or the third pixel group 853.

Next, in reference to FIG. 9 , structures adopted in focus detectionpixels 81 and 82 in yet another example will be explained. The focusdetection pixels 81 and 82 described below adopt different structureseach corresponding to the position at which a specific focus detectionpixel is disposed on the image-capturing surface 800 of the image sensor8. In other words, focus detection pixels 81 and 82 disposed in an areanear the center (e.g., in the focus detection area 810 c in FIG. 3(a))of the image-capturing surface 800 of the image sensor 8 adoptstructures different from those of focus detection pixels 81 and 82disposed in a peripheral area (e.g., in the focus detection area 810 din FIG. 3(a)) of the image-capturing surface 800.

FIG. 9(a) presents a schematic sectional view of the structures adoptedin the focus detection pixels 81 and 82 in a pixel group 850 included inthe focus detection area 810 c located near the center of theimage-capturing surface 800. A first light blocking portion 813 a, asecond light blocking portion 813 b and a third light blocking portion813 c constituting a light blocking unit 813 of the focus detectionpixel 81 in FIG. 9(a) have light blocking areas similar to those of thefirst light blocking portion 813 a in FIG. 4(c), the second lightblocking portion 813 b in FIG. 4(b) and the third light blocking portion813 c in FIG. 4(a) respectively. Likewise, a first light blockingportion 823 a, a second light blocking portion 823 b and a third lightblocking portion 823 c constituting a light blocking unit 823 of thefocus detection pixel 82 in FIG. 9(a) have light blocking areas similarto those of the first light blocking portion 823 a in FIG. 4(c), thesecond light blocking portion 823 b in FIG. 4(b) and the third lightblocking portion 823 c in FIG. 4(a) respectively.

In the focus detection pixels 81 and 82 disposed at positions at whichthey are not readily subjected to the adverse effect of vignetting,e.g., in an area near the center of the image-capturing surface 800,light having departed the photographic optical system 1 can be blocked(restricted) via their first light blocking portions 813 a and 823 a,second light blocking portions 813 b and 823 b and third light blockingportions 813 c and 823 c. Since diffraction of light and the like can beminimized by blocking light fluxes with a plurality of light blockingportions, even better light blocking performance against light fluxescan be assured. As the light blocking performance, i.e., thepupil-splitting accuracy, is improved, the accuracy of focus detectionexecuted by the focus detection operation circuit 14 can be ultimatelyimproved.

FIG. 9(b) presents a schematic sectional view of the structures adoptedin the focus detection pixels 81 and 82 in the first pixel group 851included in the focus detection area 810 d located near the periphery ofthe image-capturing surface 800. At a light blocking unit 813 of thefocus detection pixel 81, a second light blocking portion 813 b has agreater light blocking area than a first light blocking portion 813 a,and a third light blocking portion 813 c has a greater light blockingarea than the second light blocking portion 813 b.

At a light blocking unit 823 of the focus detection pixel 82, a secondlight blocking portion 823 b has a greater light blocking area than afirst light blocking portion 823 a, and a third light blocking portion823 c has a greater light blocking area than the second light blockingportion 823 b.

FIG. 9(c) presents a schematic sectional view of the structures adoptedin the focus detection pixels 81 and 82 in the third pixel group 853included in the focus detection area 810 d. At a light blocking unit 813of the focus detection pixel 81, a second light blocking portion 813 bhas a greater light blocking area than the third light blocking portion813 c, and a first light blocking portion 813 a has a greater lightblocking area than the second light blocking portion 813 b. At a lightblocking unit 823 of the focus detection pixel 82, a second lightblocking portion 823 b has a greater light blocking area than a thirdlight blocking portion 823 c, and a first light blocking portion 823 ahas a greater light blocking area than the second light blocking portion823 b.

Light having departed the photographic optical system 1 can be blocked(restricted) by the first light blocking portions 813 a and 823 a, thesecond light blocking portions 813 b and 823 b and the third lightblocking portions 813 c and 823 c at the focus detection pixels 81 and82 in the first pixel group 851 and the focus detection pixels 81 and 82in the third pixel group 853, as explained above. Since diffraction oflight and the like can be minimized by blocking light fluxes with aplurality of light blocking portions, even better light blockingperformance against light fluxes can be assured. As the light blockingperformance, i.e., the pupil splitting accuracy, is improved at thefocus detection pixels 81 and 82 in the peripheral area of theimage-capturing surface 800, the accuracy of focus detection executed bythe focus detection operation circuit 14 can be ultimately improved.

It is to be noted that the focus detection pixels 81 and 82 in thesecond pixel group 852 included in a focus detection area 810 set at theperiphery of the image-capturing surface 800 may adopt the structuresillustrated in FIG. 9(a) or the structures illustrated in FIG. 4(b).

As an alternative, the focus detection pixels 81 and 82 in the firstpixel group 851 may adopt the structures illustrated in FIG. 9(d). Eachfocus detection pixel 81 includes a light blocking unit 833 as well as alight blocking unit 813. The light blocking units 813 and 833 aredisposed on the sides facing opposite each other along the x-axis, i.e.,the light blocking unit 813 is disposed toward the + side along thex-axis and the light blocking unit 833 is disposed toward the − sidealong the x-axis. The light blocking unit 813 in FIG. 9(d) adopts astructure similar to that shown in FIG. 9(b). The light blocking unit833 includes a first light blocking portion 833 a, a second lightblocking portion 833 b and a third light blocking portion 833 c. Thedistance setting apart the second light blocking portion 833 b from themicrolens 811 is greater than the distance setting apart the first lightblocking portion 833 a from the microlens 811. The distance settingapart the third light blocking portion 833 c from the microlens 811 isgreater than the distance setting apart the second light blockingportion 833 b from the microlens 811. In addition, the second lightblocking portion 833 b has a greater light blocking area than the thirdlight blocking portion 833 c and the first light blocking portion 833 ahas a greater light blocking area than the second light blocking portion833 b. At the focus detection pixel 81 structured as described above,light having departed the photographic optical system 1 can be betterblocked by the light blocking unit 813 on the + side along the x-axisand by the light blocking unit 833 on the − side along the x-axis. As aresult, the pupil splitting accuracy is improved, which, in turn, makesit possible to improve the accuracy of the focus detection executed bythe focus detection operation circuit 14.

The focus detection pixel 82 in FIG. 9(d) includes a light blocking unit843 as well as a light blocking unit 823. The light blocking units 823and 843 are disposed on the sides facing opposite each other along thex-axis, i.e., the light blocking unit 823 is disposed toward the − sidealong the x-axis and the light blocking unit 843 is disposed towardthe + side along the x-axis. The light blocking unit 823 in FIG. 9(d)adopts a structure similar to that shown in FIG. 9(b). The lightblocking unit 843 includes a first light blocking portion 843 a, asecond light blocking portion 843 b and a third light blocking portion843 c. The distance setting apart the second light blocking portion 843b from the microlens 811 is greater than the distance setting apart thefirst light blocking portion 843 a from the microlens 811. The distancesetting apart the third light blocking portion 843 c from the microlens811 is greater than the distance setting apart the second light blockingportion 843 b from the microlens 811. In addition, the second lightblocking portion 843 b has a greater light blocking area than the thirdlight blocking portion 843 c and the first light blocking portion 843 ahas a greater light blocking area than the second light blocking portion843 b. At the focus detection pixel 82 structured as described above,light having departed the photographic optical system 1 can be betterblocked by the light blocking unit 823 on the − side along the x-axisand by the light blocking unit 843 on the + side along the x-axis. As aresult, the pupil splitting accuracy is improved, which, in turn, makesit possible to improve the accuracy of the focus detection executed bythe focus detection operation circuit 14.

It is to be noted that as an alternative to the example presented inFIG. 9(d), focus detection pixels 81 may each include a light blockingunit 813 and a light blocking unit 833 and focus detection pixels 82 mayeach include a light blocking unit 823 and a light blocking unit 843 inthe third pixel group 853. In such a case, the second light blockingportion 833 b has a greater light blocking area than the first lightblocking portion 833 a, and the third light blocking portion 833 c has agreater light blocking area than the second light blocking portion 833 bat the light blocking unit 833. In addition, the second light blockingportion 843 b has a greater light blocking area than the first lightblocking portion 843 a, and the third light blocking portion 843 c has agreater light blocking area than the second light blocking portion 843 bat the light blocking unit 843. In the focus detection pixels 81 and 82in the third pixel group 853 structured as described above, too, betterlight blocking performance is assured in much the same way as in thefocus detection pixels 81 and 82 in the first pixel group 851. As aresult, the pupil splitting accuracy is improved, which, in turn, makesit possible to improve the accuracy of the focus detection executed bythe focus detection operation circuit 14.

—Variations —

The following variations are also within the scope of the presentinvention and may be adopted in combination with the embodimentdescribed above.

FIG. 7 presents schematic plan views of focus detection pixels 81 and 82disposed in an image sensor 8 in a variation. FIG. 7(a) illustrates afirst pixel group 851, FIG. 7(b) illustrates a second pixel group 852and FIG. 7(c) illustrates a third pixel group 853. In each pixel group850, a pair of focus detection pixels 81 and 82 is disposed on one sideof each image-capturing pixel 80 with another pair of focus detectionpixels disposed on the other side instead of disposing animage-capturing pixel 80 between a focus detection pixel 81 and a focusdetection pixel 82 along the x-axis. Each pair of focus detection pixels81 and 82 share a common light blocking unit 813. The light blockingunit 813 has the same size light blocking area regardless of to whichpixel group 850 the particular pair of focus detection pixels 81 and 82belongs. Namely, a third light blocking portion 813 c in the first pixelgroup 851, the second light blocking portion 813 b in the second pixelgroup 852 and the first light blocking portion 813 a in the third pixelgroup 853 have light blocking areas of a uniform size.

The position at which the light blocking unit 813 is disposed isadjusted along the x-axis in correspondence to each pixel group 850. Inthe first pixel group 851 shown in FIG. 7(a), the third light blockingportion 813 c is disposed at a position offset by a predetermined extenttoward the + side along the x-axis relative to the position of thesecond light blocking portion 813 b in the second pixel group 852 inFIG. 7(b). In the third pixel group 853 shown in FIG. 7(c), the firstlight blocking portion 813 a is disposed at a position offset by apredetermined extent toward the − side along the x-axis relative to theposition of the second light blocking portion 813 b in the second pixelgroup 852 in FIG. 7(b). It is to be noted that a predetermined extent ofoffset may be determined by multiplying the distance to the focusdetection pixels 81 and 82, measured from the center of theimage-capturing surface 800, i.e., the image height, by a predeterminedcoefficient. In addition, if the light blocking portions are disposed atpositions having symmetry relative to the center of the image-capturingsurface 800 of the image sensor 8, the third light blocking portion 813c in the first pixel group 851 simply needs to be offset toward the −side along the x-axis and the first light blocking portion 813 a in thethird pixel group 853 simply needs to be offset toward the + side alongthe x-axis.

By assuming the structure described above, the number of requiredcomponents can be kept down.

In addition, while the selection unit 51 selects, based upon the lensinformation, a pixel group 850 optimal for the particular photographicoptical system 1 included in the photographic lens body 300 mounted atthe digital camera, among the first pixel group 851 through the thirdpixel group 853 in the embodiment described earlier, the presentinvention is not limited to this example.

For instance, the first pixel group 851 through the third pixel group853 may all be selected, and a focus detection operation may be executedby applying weight to the signals output from the optimal pixel group.For instance, the first pixel group 851 may be best suited to theparticular photographic optical system 1 and the third pixel group 853may be least suited to the photographic optical system 1. Under suchcircumstances, weight 1 may be applied to the focus detection resultsobtained by the first pixel group 851, weight 0.5 may be applied to thefocus detection results obtained by the second pixel group 852 andweight 0.1 may be applied to the focus addiction results obtained by thethird pixel group 853.

Furthermore, the focus detection operation may be executed by using twotypes of pixel groups 850, among the first pixel group 851 through thethird pixel group 853, by excluding the pixel group 850 least suited tothe photographic optical system 1.

Moreover, pixel groups 950 may be disposed with any positionalarrangement. For instance, a single type of pixel group 850 (e.g., thesecond pixel group 852) may be disposed in a central area of theimage-capturing surface 800 (e.g., near 810 c in FIG. 3 ) and threetypes of pixel groups 850 (e.g., the first pixel group 851 through thirdpixel group 853) may be disposed in a peripheral area of theimage-capturing surface 800 (e.g., near 810 a in FIG. 3 ).

As long as features characterizing the present invention remain intact,the present invention is in no way limited to the particulars of theembodiment described above and any mode conceivable within the scope ofthe technical teachings of the present invention is within the scope ofthe present invention.

The disclosure of the following priority application is hereinIncorporated by reference:

-   Japanese Patent Application No. 2015-254898 filed Dec. 25, 2015

REFERENCE SIGNS LIST

5 . . . control unit, 8 . . . image sensor, 14 . . . focus detectionoperation circuit, 15 . . . body-lens communication unit, 51 . . .selection unit, 80 . . . image-capturing pixel, 81, 823 . . . focusdetection pixel, 100 . . . digital camera, 811, 821 . . . microlens,813, 823 . . . light blocking unit, 812, 822 . . . photoelectricconversion unit, 850 . . . pixel group, 851 . . . first pixel group, 852. . . second pixel group, 853 . . . third pixel group

1. An image sensor comprising: a plurality of first pixels each having afirst photoelectric conversion unit that photoelectrically convertslight having transmitted through an optical system and a first lightblocking unit that blocks part of light entering the first photoelectricconversion unit, the plurality of first pixels outputting a first signalused for focus detection based on photoelectric conversion at the firstphotoelectric conversion unit; a plurality of second pixels each havinga second photoelectric conversion unit that photoelectrically convertslight having transmitted through the optical system and generates anelectric charge and a second light blocking unit that blocks part oflight entering the second photoelectric conversion unit, the pluralityof second pixels outputting a second signal used for focus detectionbased on photoelectric conversion at the second photoelectric conversionunit; and an output unit that outputs at least one of the first signaloutput from the plurality of first pixels and the second signal outputfrom the plurality of second pixels based on at least one of informationon a position of an exit pupil of the optical system and information ona distance of the exit pupil.
 2. The image sensor according to claim 1,wherein the first light blocking unit is provided at a first distancefrom the first photoelectric conversion unit, and the second lightblocking unit is provided at a second distance that is different fromthe first distance from the second photoelectric conversion unit.
 3. Theimage sensor according to claim 1, wherein the first pixel includes afirst microlens, and the first photoelectric conversion unitphotoelectrically converts light having transmitted through the firstmicrolens; the second pixel includes a second microlens, and the secondphotoelectric conversion unit photoelectrically converts light havingtransmitted through the second microlens; and a distance between thefirst microlens and the first light blocking unit is different from adistance between the second microlens and the second light blockingunit.
 4. The image sensor according to claim 1, wherein an area of thefirst light blocking unit is different from an area of the second lightblocking unit.
 5. The image sensor according to any of claim 1, whereina light blocking area by which the first light blocking unit blockslight is different from a light blocking area by which the second lightblocking unit blocks light.
 6. The image sensor according to claim 1,wherein the first pixel receives light having transmitted through afirst region of the optical system, and the second pixel receives lighthaving transmitted through a second region of the optical system, thesecond region being different from the first region.
 7. The image sensoraccording to claim 1, wherein an amount of light that the firstphotoelectric conversion unit photoelectrically converts is differentfrom an amount of light that the second photoelectric conversion unitphotoelectrically converts.
 8. The image sensor according to claim 1,wherein an area of the first light blocking unit included in each of atleast two first pixels among the plurality of first pixels is differentdepending on a position of an image-capturing surface, and an area ofthe second light blocking unit included in each of at least two secondpixels among the plurality of second pixels is different depending on aposition of the image-capturing surface.
 9. The image sensor accordingto claim 8, wherein an area of the first light blocking unit included inthe first pixel located near a center of the image-capturing surfaceamong the plurality of first pixels is smaller than an area of the firstlight blocking unit included in the first pixel located near an edge ofthe image-capturing surface, and an area of the second light blockingunit included in the second pixel located near the center of theimage-capturing surface among the plurality of second pixels is smallerthan an area of the second light blocking unit included in the secondpixel located near the edge of the image-capturing surface.
 10. Theimage sensor according to claim 1, wherein a number of the first pixelsis different from a number of the second pixels.
 11. The image sensoraccording to claim 1, wherein the first light blocking unit is a firstcircuit wiring disposed in the first pixel, and the second lightblocking unit is a second circuit wiring disposed in the second pixel.12. An image-capturing device comprising: the image sensor according toclaim 1; and a control unit that controls a position of the opticalsystem to a focal position at which an image by the optical systemachieves an in-focus state at the image sensor based on at least one ofthe first signal output from the plurality of first pixels and thesecond signal output from the plurality of second pixels.
 13. Theimage-capturing device according to claim 12, further comprising: areception unit that receives, from an interchangeable lens having theoptical system, at least one of the information on the position of theexit pupil of the optical system and the information on the distance ofthe exit pupil.